In general, a suspension system prevents a vehicle from jolting due to vibration accompanied by a noise that is generated by roughness of the road while the vehicle travels.
The suspension system commonly includes a spring, a shock absorber, a stabilizer, and a control arm and improves a comfortable ride and stability of the vehicle by making three functions of adjusting a spring coefficient, a damping force, and the vehicle height.
Further, the control arm of the components of the suspension system is transversely disposed in the vehicle, that is, of which an end is fastened to a knuckle (or carrier) of a wheel through a bush and the other end is fastened to a cross member (or subframe) through a bush, such that it has rigidity against inward/outward loads as well as the forward/backward loads of the vehicle, which are transmitted through the knuckle of the wheel.
The control arm is generally made of a steel, but, at present, it tends to be made of aluminum that is useful to structural products for the most stable physical properties and is manufactured by extrusion molding for the properties of the aluminum.
For example, in order to connect an extruded straight-hollow aluminum member that has undergone cold bending to the carrier (to wheel) and to the subframe (to car body), a control arm is bent and then molded by a press to fasten a bush and a carrier. Thereafter, a hole is formed through the control arm molded in a control arm shape and the bush is assembled.
However, according to the extrusion molding of the control arm of aluminum, since the extruded straight member should undergo bending and molding, for example, a process to secure good molding of the member by solution heat-treatment before molding is required to prevent breakage when forming a bush fastening portion and a carrier fastening portion, the manufacturing process becomes complicated and the manufacturing cost relatively increases.
In particular, since extruding and bending processes that are earlier process for machining the raw material of aluminum are separated, more time is required for extrusion molding and productivity to the entire manufacturing process decreases.